For her postdoctoral research at BIOS, oceanographer Sheryl Murdock collaborates with her former University of Victoria laboratory colleague, Damian Grundle, now a BIOS faculty member.
When Sheryl Murdock’s young daughters came to visit Bermuda from western Canada this spring, they were smitten by the clear turquoise waters surrounding the island and awed that they could see all the way to the sandy ocean bottom as they waded along local beaches. “They kept saying ‘it’s so clear, there’s nothing in there,’” Murdock said. “And I kept saying, ‘there’s not nothing in there. It’s full of life you can’t see—microbes.’”
Murdock, 47, calls microbes the engines of the ocean. They’re responsible for feeding other sea life, breaking down waste, making oxygen, and absorbing carbon dioxide. These tiny creatures, among the oldest living organisms on Earth, range from algae and bacteria to fungi and plankton. In Murdock’s early teens she saw a National Geographic magazine featuring newly-discovered deep-sea hydrothermal vents teeming with giant clams, tubeworms, and other marine life supported by nutrient-providing microbes. Since then, those ecosystems have been objects of her fascination.
Recently, she has shifted her research to the relatively shallow waters of Saanich Inlet, a fjord near her home in British Columbia. Over the next two years, she will travel between there and Bermuda to conduct her National Science Foundation (NSF)-funded postdoctoral research, focusing on the marine microbes that live under low-oxygen conditions in the cold waters of the inlet.
Last summer, project collaborators and scientists Brett Jameson (right) of the University of Victoria and Laura Bristow of the University of Southern Denmark conducted initial water sampling in Saanich Inlet, a fjord in British Columbia. Marine microbes that live there under low-oxygen conditions are the subject of Murdock’s postdoctoral research with BIOS. Photo by Sheryl Murdock
Postdoctoral research with BIOS
Murdock joined BIOS in February 2022 as a postdoctoral researcher funded through an NSF grant awarded to faculty member Damian Grundle, whose laboratory she will be working in. Grundle, a chemical oceanographer, studies nitrogen cycles in the ocean, and how some forms of this essential life ingredient, in excess, can contribute to climate change.
Both Murdock and Grundle, who met through their laboratory connections at the University of Victoria in British Columbia and had the same advisor for their doctoral work (biologist S. Kim Juniper), investigate the chemical compound nitrous oxide. This gas, more commonly known as laughing gas, is both produced and consumed by different groups of microbes and is the third most potent greenhouse gas, after carbon dioxide and methane.
The potential for nitrous oxide to accumulate and contribute to climate change depends not only on microbes, but also on levels of oxygen in the ocean. Murdock is interested in identifying the specific microbes responsible for nitrous oxide production and consumption, as well as measuring the rates of both these processes in zones where oxygen levels reach near-zero values, an environmental state called anoxia.
These low oxygen and anoxic zones favor production of nitrous oxide and are of particular interest to scientists, Murdock said, because they are expanding, in part, due to climate change and overuse of agricultural fertilizers
“Saanich Inlet, which has annual cycles of anoxia, is an ideal natural laboratory for this study,” she said.
In the ocean, the balance of nitrous oxide production and consumption is largely controlled by the amount of available dissolved oxygen, with more produced under low oxygen concentrations. However, when no oxygen is available, microbes in the ocean switch from producing nitrous oxide to consuming nitrous oxide. In recent years, Murdock said, it has become evident that zones of low oxygen are expanding in some areas of the ocean. This has raised concern that more nitrous oxide will be produced.
“If this occurs, more nitrous oxide could be emitted to the atmosphere, and may lead to further global warming and ozone destruction,” Murdock said. More robust data will help inform the models scientists use to predict oceanic nitrous oxide production and emissions to the atmosphere under future climate conditions.
Work has begun
In March, Murdock began traveling between Grundle’s lab at BIOS and Canada, where she lives with daughters Kira, 14, and Simone, 12. There, she also has access to laboratory space at the University of Victoria, where she worked as a lab technician and manager for eight years before completing her PhD.
This month, Murdock, Grundle, and collaborating team members from Montana State University and the University of Southern Denmark will be conducting their second field sampling campaign in Saanich Inlet. Last summer, the team collected water samples from several oxygenated and anoxic depths for measuring rates of production and consumption, along with samples for DNA analysis.
Corresponding measurements of temperature, salinity, and nutrients (such as nitrate and phosphate) were made aboard University of Victoria-owned research vessel John Strickland. This year, their goal is to run additional experiments to develop a greater understanding of the controls on microbes involved in nitrous oxide cycling.
‘Weird of the world’
Murdock grew up in Seattle in a family of science fiction enthusiasts who she said “had an interest in the weird of the world.” In the late 1970s, she saw the first photos to emerge of hydrothermal vents 400 miles (640 kilometers) off the South American coast near the Galapagos Islands. Far below the reach of sunlight, scientists found thriving yet alien-like life associated with the shimmering, super-heated plumes of mineral-laden seawater that percolates through volcanic subsurface rocks.
The abundant life, including tubeworms and giant clams that are unique to these extreme habitats, are supported by chemical transformations performed by microbes and fueled by the mineral-rich hydrothermal fluids.
“I thought hydrothermal vents were the coolest and weirdest thing on Earth,” she said. When she attended the University of Washington as an undergraduate to study biological oceanography, and later for work in university labs in Seattle as well as at the University of Victoria, her work was rooted in the deep sea. She specifically focused on understanding the microbial ecology of hydrothermal vents.
In recent years, she has become interested in understanding connections between biological components of ecosystems and how each contributes to the functioning of the ecosystem as a whole. Organisms like microbes and larger animals like plankton and larval fish are studied separately despite living together. Murdock’s recent work has focused on identifying ‘core communities’ of organisms, from large to microscopic, that may be collectively important for how an ecosystem operates.
She says that understanding the connections between organisms and the functions of each can improve models of how ecosystems respond to stress. During her PhD work, she identified core communities of microbes and animals in hydrothermal vent tubeworm habitats and is currently trying to understand how the various community members may support each other.
In the future she hopes to further explore her interest in international policy, specifically in relation to regulations surrounding deep-sea mining and other activities that may disturb hydrothermal vents and other unique deep-sea environments. Her hope is to work with policy makers and conservation managers to share what she is learning and guide future development of monitoring and management strategies for sensitive marine habitats.
“It’s appealing to me to apply my research in a way that can inform our human decision making and activities moving forward,” she said.